1. Field of the Invention
The present invention relates to a fuel cell system provided with a fuel cell including an anode electrode and a cathode electrode disposed opposingly with an electrolyte interposed therebetween, for obtaining electromotive force by supplying fuel gas containing hydrogen to the anode electrode while supplying oxygen-containing gas containing oxygen to the cathode electrode. The present invention also relates to a gas/liquid separation method for the same.
2. Description of the Related Art
The fuel cell stack, which is constructed, for example, by stacking a plurality of fuel cells each comprising an anode electrode and a cathode electrode disposed opposingly with a solid polymer ion exchange membrane interposed therebetween, the fuel cell being interposed between separators, has been developed, and it is being practically used for a variety of applications.
Such a fuel cell stack is designed as follows. That is, for example, a reformed gas (fuel gas), which contains a hydrogen-containing gas produced by reforming a mixture liquid (aqueous methanol solution) composed of water and liquid fuel such as methanol, is supplied to the anode electrode. An oxygen-containing gas (air or gas containing oxygen) is supplied to the cathode electrode. Thus, the hydrogen gas is ionized, while it flows through the solid polymer ion exchange membrane. Accordingly, electric energy is obtained at the outside of the fuel cell stack.
The fuel cell stack is provided with a condenser for condensing discharged components discharged from the fuel cell stack and separating them into gas components and water. Recovered water, which is produced by the condenser, is used, for example, as reforming water. Those known as such a technique include, for example, a condensed water recovery apparatus disclosed in Japanese Laid-Open Patent Publication No. 6-176784.
In this conventional technique, the temperature of cooling water supplied to a condensing heat exchanger is measured. A flow rate control valve, which is provided for a bypass piping tube, is controlled depending on an obtained measured value to control the flow rate of warm water to be mixed with the cooling water. Thus, the temperature of the cooling water flowing through the condensing heat exchanger is maintained to be constant. Accordingly, the flow rate of the cooling water supplied by a constant flow pump to the condensing heat exchanger is maintained to be constant, while the amount of heat exchange effected by the condensing heat exchanger is made constant so as to obtain a constant amount of recovered water of the condensing heat exchanger purified by an ion exchange processing apparatus.
However, in the case of the conventional technique described above, the amount of cooling water supplied to the condensing heat exchanger is constant. For this reason, it is necessary to ensure an amount of cooling water so that the discharged components may be sufficiently condensed, corresponding to the process in which the amount of discharged water discharged from the fuel cell stack is increased, i.e., corresponding to the process in which the output of the fuel cell stack is increased. Therefore, the amount of cooling water is set to be a considerably large amount. Even when the output of the fuel cell stack is low, it is necessary to maintain the large amount of cooling water. As a result, such a problem is pointed out that the current consumption of the pump is unnecessarily increased.
A principal object of the present invention is to provide a fuel cell system which makes it possible to efficiently condense discharged components and obtain a desired amount of recovered water so that the current consumption of a pump is effectively reduced, and a gas/liquid separation method for the same.
The above and other objects, features, and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings in which a preferred embodiment of the present invention is shown by way of illustrative example.